Electrostatic forces have been used to levitate objects. Shao Ju Woo, Jong Up Jeon, Toshiro Higuchi, and Andreas Stemmer discuss in their article “Hysteretic Feedback Control of Electrostatic Levitator for Objects Possessing Large Suspension Area-Airgap Ratio” the electrostatic levitation of 4-inch silicon wafers utilizing a one degree of freedom electrostatic levitator.
Michael Kraft, et. al., of the University of Southampton discuss in their article “System Level Simulation of an Electrostatically Levitated Disk” (hereinafter Kraft) simulating the levitation of a micromachined disk by using sigma delta feedback control. Kraft discusses using a middle electrode, which is surrounded by four additional electrodes, to control pitch and tilt. The set of electrodes is above and beneath the disk; therefore, there is the need for up to eight control circuits. Kraft measures the distance of the disk. When the disk leaves a designated position, the maximum force is switched on. This will cause the disk to return to the designated position. Since the maximum force is switched on, the disk will leave the designated position moving in the opposite direction. This will cause the opposite voltage to switch on to force the disk to return to designated position under the influence of a force opposing the first force. Therefore, the disk will always receive high force impulses and the mass of the disk is used to hold the movement of the disk low. The mass of the disk may be 1000 ug. In Kraft, if an external force is applied to the disk (acceleration) the frequencies of the force peaks will change, and this is used to measure the external force.
Tokimec, Inc. discusses in “Inertia Sensor Performing Measurement with Rotor Levitating in Vacuum” (hereinafter Tokimec) a sensor which is able to measure the angular rate and acceleration. The Tokimec sensor is a free-floating rotational disk made out of Pyrex glass.
However, there is a need for a micromechanical device for measuring acceleration, angular acceleration, angular velocity, and/or tilt using an electrostatic levitated disk, with a minimum amount of control circuitry.